Increasingly, implantable active medical device systems are being used or investigated for use in treatment protocols or other therapies for a variety of neurological conditions or disorders. For example, implantable active medical device systems are known that rely upon an implanted pulse generator (IPG) or neurostimulator in operable communication with one or more electrodes (such as via electrode-bearing leads) to deliver a form of electrical stimulation (e.g., charge-balanced pulsatile stimulation) to the neural tissue of a patient. The stimulating elements and the form of stimulation may be configured based on the specific application of the system.
For example, electrodes may be implanted at or near particular anatomical structures or in particular neural circuits in a patient's brain and the stimulation parameters (e.g., amplitude and duration) may be optimized for addressing the symptoms of a movement disorder such as Parkinson's disease (e.g., tremor or bradykinesia). Similarly, electrodes may be located at deep brain structures that are understood to be related to major depressive disorder (MDD) and the parameters governing the stimulation selected to alleviate the condition. Many other potential applications of neurostimulation are being explored for addressing a wide variety of conditions or disorders understood to have a neurological connection, ranging from gastrointestinal disorders like gastroesophageal reflux disease (GERD) and obesity to migraine headaches. Still other applications of implantable active medical device systems include encouraging recovery of the brain from stroke.
Active implantable medical device systems have been used in clinical trials for patients with epilepsy in which an implanted neurostimulator may be configured to monitor electrographic signals sensed on one or more channels using sensing elements (such as macroelectrodes) that are implanted in or on the patient's brain. The neurostimulator further may be configured to process the sensed signals and to recognize one or more patterns occurring in the signals. The neurostimulator may have a variety of tools or algorithms that can be programmed to recognize certain patterns or sequences or other combinations of patterns when they occur in the sensed signals as “events.” A given event may be understood to be related in some way to the patient's epilepsy (e.g., an event may be categorized as a precursor to a seizure or as a “seizure onset” or as a fully developed seizure). Additionally, the neurostimulator may be configured to generate and deliver through one or more stimulation elements a form of electrical stimulation therapy whenever it detects a particular event or events. Since in this system the neurostimulator can be configured to respond to events by delivering stimulation, the system is referred to as a responsive neurostimulation system. Once such responsive neurostimulation system is manufactured under the tradename the “RNS SYSTEM” by NeuroPace, Inc.
In many implantable neurostimulator systems, one or more external components may be configured for selective communication with the implanted neurostimulator (e.g., using inductive telemetry). A “programmer” is the name commonly used to refer to one of these external components, and it is used by a patient's physician to initially program or to reprogram the operating parameters of the neurostimulator). A programmer also may be configured to assess a state or condition of the neurostimulator (e.g., whether the neurostimulator is enabled to deliver stimulation or how much remaining life there is on the neurostimulator's primary cell or rechargeable battery). If the neurostimulation system is a responsive one and therefore one that acquires anti/or stores information sensed from the patient, then the programmer may also be used to interrogate the neurostimulator as to data the neurostimulator either has stored or is receiving in real time corresponding to the sensed signals.
A “remote monitor” is the name commonly used to refer to another of these external components, and it is used by the patient to communicate with the neurostimulator and to accomplish some limited set of functions (e.g., to disable stimulation, to cause the neurostimulator to store a record corresponding to a sensed signal at a time when the patient subjectively believes an “event” or a seizure might be occurring, and to download data from the neurostimulator so that it can be directed to a centralized database where the patient's physician can review it and perhaps otherwise manipulate it).
Electrical stimulation thus is an established therapy for treating some neurological disorders and responsive electrical stimulation is an emerging therapy for treating epilepsy and may be useful in treating other disorders and conditions. In responsive neurostimulation, delivery of therapy is triggered in response to information acquired about a physiological condition of a particular location or locations in or on the patient's brain (e.g., field potential measurements acquired from electrodes implanted at or near what is understood to be a focus of epileptiform activity for the patient). It will be appreciated that the success of a particular electrical stimulation therapy, at least to some degree, may be related to the quality and quantity of the physiological information that is relied upon to trigger that therapy. Moreover, this is likely to be the case regardless of which neurological disorder or condition the therapy is intended to treat (e.g., epilepsy, migraine headaches, movement disorders, etc.).
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